I think you might be ok using
Felicity with
Joy. Not many people use "felicitation" as a word in English anymore. I don't know how many would know what it means.
Serenity on the other hand is very obvious.
Your set of
Felicity,
Caitlin and
Joy is really nice.
Cassandra,
Serenity and
Joy makes
Serenity look like the odd one out.